Agricultural Engineering Research Journal 5(3): 33-41, 2015 ISSN 2218-3906 © IDOSI Publications, 2015 DOI: 10.5829/idosi.aerj.2015.33.41 Corresponding Author: Dr. Majid Rashidi, Ph.D., Agricultural Engineering Research Department, Tehran Agricultural and Natural Resources Research Center, AREEO, Varamin, Iran. E-mails: majidrashidi81@yahoo.com & m-rashidi@areeo.ac.ir. 33 Modeling of Soil Pressure-Sinkage Behavior Using the Finite Element Method Majid Rashidi, Reza Attarnejad, Ahmmad Tabatabaeefar and Alireza Keyhani 1 2 3 3 Agricultural Engineering Research Department, Tehran Agricultural 1 and Natural Resources Research Center, AREEO, Varamin, Iran Civil Engineering Department, Faculty of Engineering, University of Tehran 2 Power and Machinery Department, Faculty of Agricultural Biosystem Engineering, University of Tehran 3 Abstract: The finite element method (FEM) is a useful tool in the development of model for soil pressure- sinkage behavior and can be used to investigate and analyze the soil compaction. For this purpose, the finite element method was used to model soil pressure-sinkage behavior and a two-dimensional finite element model was developed to perform required numerical calculation. This program was written in FORTRAN. The soil material was considered as an elastoplastic material and the Drucker-Prager elastoplastic material model was adopted with the flow rule of associated plasticity. In order to deal with material non-linearity, incremental method was adopted to gradually load the soil and a total Lagrangian formulation was used to allow for the geometric non-linear behavior of soil. The FEM model was verified against previously developed models for one circular footing problem and one strip footing problem and the finite element program was used to predict the pressure-sinkage behavior of soil under footings. The statistical results of the study confirmed the validity of the FEM model and demonstrated the potential use of the FEM in prediction of soil pressure-sinkage behavior. Key words: Finite element method Pressure-sinkage Drucker-prager Elastoplastic Soil compaction INTRODUCTION Most studies dealing with soil sinkage have been Agronomists are concerned about the effects of procedure is that it is laborious, time consuming and heavy tractors and agricultural machines on agricultural expensive. An alternative approach is to develop a soils due to the possibly of excessive soil compaction that numerical technique that can predict soil pressure-sinkage impedes root growth and hence reduces crop yields [1]. behavior. One such technique that can be used to predict Soil compaction under tractors and farm machinery is of soil sinkage is the finite element method (FEM). The FEM special concern because the weight of these machines has is now firmly accepted as a most powerful general been increased dramatically in the last few years [2] and technique for the numerical solution of a variety of these implements create persistent subsoil compaction [3]. problems encountered in engineering. Applications range One of the most important causes of soil compaction is from the stress analysis of solids to the solution of the soil response to pressure and sinkage imposed by acoustical, neutron physics and fluid mechanics wheels and tracks [2]. Therefore, the prediction of soil problems. Indeed the FEM is now established as a general sinkage under loads is very important for determining the numerical method for the solution of problems subjected level of compaction in the soil. Furthermore, the ability to to known boundary and/or initial value conditions. predict soil sinkage can enable agricultural engineers to The basic concept of the FEM is the idealization of the till or traffic the soil when it is not in a highly compatible continuum as an assemblage of a finite number of state or to estimate the damage being done to the soil elements or small segments interconnected at nodal structure due to their excessive loading when tillage or points. The behavior of the continuum when loaded is traffic is necessary [4]. then predicted by approximating the behavior of the experimental. One disadvantage of the experimental